The invention relates to a television camera in which a color splitting prism and a number of pick-up tubes are positioned with respect to each other, in a holder which comprises an annular seat for the optical alignment of each pick-up tube, each pick-up tube being pressed onto said respective seat, by way of an adapter ring which is connected to the tube transversely of the tube axis by means of a resilient pressure member which acts in the direction of the tube axis. The invention also relates to a pick-up tube which is suitable for use in a camera of this kind and which comprises a cylindrical, glass tube which is sealed at one end by an end wall wherethrough electrical connections are passed, and on the other end by a light-admitting entrance window which is directed transversely of the tube axis.
Netherlands Patent Application No. 76.11.284, which corresponds to co-pending U.S. patent application Ser. No. 835,632, filed Sept. 22, 1977, now abandoned, describes a television camera of the kind set forth in which the holder comprises cylindrical openings for three pick-up tubes. In each of the openings there is provided an annular seat comprising, viewed in the direction of the tube axis, an axial and a radial reference face. In a jacket bushing, each pick-up tube forms one unit with a mumetal bushing and a coil unit and is pressed, by way of an end of the jacket bushing which is to be considered as an adapter ring, into a seat against the axial reference face. In the radial sense, the end of the jacket bushing to be considered as an adapter ring is located by the radial reference face in the seat.
In the known camera, the seat in the holder opening, as well as the part of the jacket bushing of the tube unit to be considered as an adapter ring, is provided with an axial and a radial reference face, viewed in the direction of the tube axis. For accurate and stable positioning of the pick-up tube in the holder, the radial and the axial reference faces must be accurately formed to be exactly perpendicular to each other, which requires difficult and expensive operations. Moreover, in order to allow the pick-up tube to be mounted in the seat, a given play between the jacket bushing and the radial reference face of the seat is required. Mechanical shocks, occurring notably and frequently when the tubes are used in portable cameras, are liable to change the position of the pick-up tubes in the seats in the holder as a result of this radial play. Consequently, the optical positions of picture rasters to be scanned on the photosensitive layers of the pick-up tubes will also change with respect to each other, thus giving rise to picture registration errors. These picture registration errors occur notably in television cameras utilizing small pick-up tubes with a picture raster having a very small surface area. If this surface area is, for example, 5.6.times.4.2 mm.sup.2, in the case of imaging by means of 625 lines, a very small shift of a few .mu.m causes a picture shift which is so annoying that electronic readjustment of the picture registration is necessary.